System and method for transmit signal pulse shaping in automotive applications

ABSTRACT

A system and method for transmit signal pulse shaping in automotive applications. Automotive vehicle manufacturers that incorporate electronic components into an automotive vehicle must consider emission requirements masks that can be dependent on particular geographic markets as well as the other electronic components contained within a particular automotive vehicle design. A physical layer device is provided that can be configured to operate in multiple emissions configurations using configurable parameters specified for the modulation and wave shaping modules.

BACKGROUND

1. Field of the Invention

The present invention relates generally to pulse shaping and, moreparticularly, to a system and method for transmit signal pulse shapingin automotive applications.

2. Introduction

Automotive vehicles have become increasingly complex, incorporatingdramatically increasing amounts of electronics content. This trend isexpected to continue into the foreseeable future as automotive vehiclesincorporate and interoperate with a variety of electronic devices. Forexample, automotive vehicles have incorporated increasing numbers ofelectronic control units (ECU) for the operation of the automotivevehicle itself, as well as incorporating or interoperating withincreasing numbers of devices that support mobile communications,entertainment and navigations systems, security systems, or the like inthe automotive vehicle.

This growth in the amount of electronics content within an automotivevehicle has created a greater need in examining the impact of theelectromagnetic emissions generated by those various electronics-basedsystems. Not only are these electromagnetic emissions significant in thecontext of the vehicle itself, but they are also significant in thecontext of their impact on systems that are external to the automotivevehicle. As would be appreciated, unchecked electromagnetic emissionsgenerated by electronics within an automotive vehicle can negativelyimpact the operation of roadside equipment. This impact cannot be viewedfrom the perspective of a single automotive vehicle. Rather, this impactmust be viewed in the context of a fleet of automotive vehicles that areoperating on a road network.

Automotive vehicle manufacturers typically develop their own internalstandards that enables them to manufacturer automotive vehicles that canmeet the requirements of the various geographic markets in which theirautomotive vehicles are sold. These varying requirements can place asignificant burden on the automotive vehicle manufacturers as they seekto reduce production costs for the various manufacturing components.

What is needed therefore is a mechanism that enables a manufacturer toflexibly tailor a solution to a particular set of emissions and noiserequirements that are designed to limit the impact on on-board equipmentas well as external equipment.

SUMMARY

A system and method for transmit signal pulse shaping in automotiveapplications, substantially as shown in and/or described in connectionwith at least one of the figures, as set forth more completely in theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered limiting of its scope, the invention will be describedand explained with additional specificity and detail through the use ofthe accompanying drawings in which:

FIG. 1 illustrates an example of a emission requirement mask for anautomotive application.

FIG. 2 illustrates an embodiment of a mechanism that enablesprogrammable control of emissions and noise.

FIG. 3 illustrates an example of a wave shaping filter.

FIG. 4 illustrates an example of a normalized power spectral densityusing configurable wave shaping.

FIG. 5 illustrates a flowchart of a process of the present invention.

DETAILED DESCRIPTION

Various embodiments of the invention are discussed in detail below.While specific implementations are discussed, it should be understoodthat this is done for illustration purposes only. A person skilled inthe relevant art will recognize that other components and configurationsmay be used without parting from the spirit and scope of the invention.

Data communication devices built for automotive vehicle applications aresubject to meeting certain emission requirements. FIG. 1 illustrates anexample of an emission requirement mask that can be used as a designguide in an automotive vehicle application. In general, the emissionrequirement mask defines an interference voltage level over a frequencyspectrum. In the example of FIG. 1, the emission requirement maskdefines a more restrictive interference voltage level in the higherfrequency range as compared to the lower portion of the frequencyspectrum.

Emission requirement masks that can be applied to a particularautomotive vehicle system design can vary significantly. This can bedue, for example, to the particular target geographical region in whichthe automotive vehicle will operate. As some geographical regions wouldrequire more restrictive emission requirements, a range of emissionrequirement masks can therefore result. As a practical matter, thisrange of emission requirement masks can lead to either an overlyrestrictive design that is applied to multiple geographic markets, or tomultiple specialized designs that are individually targeted toparticular geographic markets.

The design process for a given emission requirement mask can alsoencounter numerous challenges. More specifically, a physical layerdevice (PHY) that is designed for use in an automotive application canbe called upon to support various types of installations represented bydifferent manufacturers. For example, the different manufacturers canuse different types of cabling (e.g., twisted pair, optical, etc.) tointerconnect the electronic systems. As would be appreciated, emissioncontrol can be particularly important when a manufacturer decides to useunshielded copper cables.

Many additional factors beyond the geographic market and the type ofcabling used can impact the emission requirements. For example, factorssuch as the automotive vehicle body design, the location of the cabling,and other electronic equipment used in the same automotive vehicle canimpact the desired emission limits that are applied to a particularautomotive vehicle. For these reasons, a single emission requirementmask is unlikely to be applied.

It is a feature of the present invention that the existence of multipleemission requirement masks can be accommodated by a flexible PHY designthat can be configured to meet a particular emission requirement mask.This configurability enables a PHY design to be applied across multipleautomotive vehicle manufacturers, as well as applied to multipleemission requirement design scenarios for a particular automotivevehicle manufacturer.

Reference is now made to FIG. 2, which illustrates an example of a PHYthat enables programmable control of emissions and noise. As illustratedin FIG. 2, the PHY includes modulator 202 that modulates a carriersignal based on incoming data. In one embodiment, modulator 202 is apulse amplitude modulation (PAM) modulator. In the present invention,modulator 202 can have the capability to operate at multiple transmitsymbol rates, multiple transmit power levels, and multiple modulationlevels.

The modulated signal generated by modulator 202 is passed to waveshaping module 204. To attain maximum noise immunity while reducingemission in higher frequency range, wave shaping module 204 generates acustom transmit signal that shapes the spectrum of the transmit signalto the emissions requirement mask. Here, it should be noted that withoutproper spectral shaping, the transmit signal level would have to bereduced to pass a particular emission mask. This flat power reductionwould have significant limitations, however, when considering its impacton noise immunity and cable reach.

The custom transmit signal generated by wave shaping module 204 ispassed to digital-to-analog converter (DAC), which passes the analogtransmit signal to line driver 208 for transmission to receiver. Aswould be appreciated, the receiver can include a fixed/adaptive inversefilter corresponding to the wave shaping function to assist in thereceiver's decision-point signal-to-noise ratio (SNR) optimization

Wave shaping module 204 is designed to implement a particular waveshaping function that can shape the transmit signal as needed. In oneexample, the wave shaping function is represented by a programmabledigital filter of the form:F(z)=a+z ⁻¹

FIG. 3 illustrates the normalized frequency response for this filter fora=3 and a=2. As illustrated, the filter provides 6 dB or 9.5 dBrejection at the Nyquist frequency (i.e., half of the transmit symbolrate). Other wave shaping functions can be implemented by wave shapingmodule 204 as would be appreciated without departing from the scope ofthe present invention.

FIG. 4 shows the normalized power spectral density (PSD) for an exampleconfiguration. In this example, the symbol rate is 133.3 MHz and the PSDis shown for three selection of filter coefficients (i.e., a=0, 2, 3).For a =0 there is essentially no shaping applied through the digitalfilter. For a=2, 3, the Nyquist frequency at 66.7 MHz provides spectralshapes with better matching to the emission requirement mask such asthat illustrated in FIG. 1.

As would be appreciated, further shaping of the PSD can be achieved byusing analog filters either on chip or off chip. For example, passivefilters that follow line driver 208 can be used on the board for aparticular system data rate to allow further reduction of transmit PSDside lobes or edges of the main lobe if needed.

As further illustrated in FIG. 2, control of modulator module 202, waveshaping module 204, phase locked loop (PLL) 208, and line driver 210 iseffected by PHY control 212. In the present invention, the controlapplied by PHY control 212 over modulator 202 and wave shaping module204 enables a PHY design that can be configured to provide customizedwave shaping to fit a particular emission requirement mask.

Here, it is recognized that the selection of a wave shaping function forapplication by wave shaping module 204 can be based on a selection of afixed wave shaping function and/or a selection of one or morecoefficients of a variable wave shaping function. The selection of aparticular wave shaping function for application by wave shaping module204 is based on control registers 214.

In general, control registers (e.g. non-volatile memory) can be designedto store parameters that can be used by PHY control 212. In the exampleof a PAM modulator, the stored parameters can be used by PHY control 212to control a transmit symbol rate, a transmit signal level (or power)and PAM modulation type (and optionally coding) that is implemented bymodulator module 202. The stored parameters can also be used by PHYcontrol 212 in controlling wave shaping module 204. For example, thestored parameters can be used to select a particular wave shaping format(if more than one filter type is used) and wave shaping coefficients fora particular wave shaping format. Still further, the stored parameterscan be used to configure PHY control 212. For example, the storedparameters can be used to direct the changes in configuration at thevarious stages of PHY control.

In combination, parameters stored in control registers 214 can be usedby PHY control 212 to tailor a PHY to satisfy a particular emissionrequirements mask that is defined for a particular vehicle. As theoptimum solution for one vehicle may not be the same as another vehicle,control registers 214 provide a look-up table based mechanism by which aPHY can be customized for the particular settings that are desired for aparticular automotive vehicle for a particular automotive vehiclemanufacturer.

Having described an example implementation of a PHY that incorporatesconfigurable wave shaping, reference is now made to the flowchart ofFIG. 5, which illustrates an example process of the present invention.As illustrated, the process begins at step 502 where parameters aredefined for multiple emissions configurations. In general, it isdesirable to apply the multiple emissions configurations of a single PHYdesign to multiple emissions requirements masks used by an automotivevehicle manufacturer.

In one embodiment, each of the multiple emissions configurations aredefined through the identification of a unique set of configurableparameter values. As noted above, the set of configurable parameters caninclude parameters that define the transmit symbol rate, the transmitsignal level (or power), the modulation type (and optionally coding),the wave shaping format, the wave shaping coefficients, and the PHYcontrol configuration. In a simple example, two different emissionsconfigurations can be defined where a first emission configuration has awave shaping coefficient having a first value (e.g., a=2), and a secondemission configuration has a wave shaping coefficient having a secondvalue (e.g., a=3).

In the process of step 502, a particular combination of configurableparameter values is defined to target each defined emissions requirementmask. The resulting multiple combinations of configurable parametervalues would then be stored in the configuration registers accessible bythe PHY at step 504. The storage of the configurable parameter values inthe configuration registers would enable the PHY to be configurable foractive operation in a particular emissions configuration.

More specifically, at step 506, the PHY control would identify aparticular PHY emissions configuration that should be used by the PHY.In one embodiment, the identification of the particular PHY emissionsconfiguration to be used can be based on a PHY control configurationparameter that identifies one of the set of emissions configurationsthat the automotive vehicle manufacturer desires to use in thatapplication.

Based on such an identified PHY emissions configuration, the PHY controlcan then configure the PHY using the configuration parameters retrievedfrom the configurations registers. For example, the PHY control canconfigure the modulation module to operate at a specific transmit symbolrate, transmit signal level (or power), and modulation type (andoptionally coding) based on the retrieved configuration parameters, andconfigure the wave shaping module to operate with a particular waveshaping format and wave shaping coefficients based on the retrievedconfiguration parameters.

As has been described, the configurability of the PHY to accommodatevarious emissions configurations provides significant flexibility to theautomotive vehicle manufacturer in implementing an electroniccommunications component within a particular automotive vehicle. Such adesign process is heavily dependent on the target geographical market aswell as other electronic components to be included. As a designrepresents an evolutionary process, the provision of a flexible designtool enhances the ability of the automotive vehicle manufacturer tocontrol the resulting emissions requirements of the automotive vehicleas a whole.

These and other aspects of the present invention will become apparent tothose skilled in the art by a review of the preceding detaileddescription. Although a number of salient features of the presentinvention have been described above, the invention is capable of otherembodiments and of being practiced and carried out in various ways thatwould be apparent to one of ordinary skill in the art after reading thedisclosed invention, therefore the above description should not beconsidered to be exclusive of these other embodiments. Also, it is to beunderstood that the phraseology and terminology employed herein are forthe purposes of description and should not be regarded as limiting.

What is claimed is:
 1. A method in a physical layer device forcontrolling radiated emissions in a data network application in anautomotive vehicle, comprising: retrieving, by a control module in saidphysical layer device, configuration parameters from a control register;configuring, by said control module, a transmit symbol rate and atransmit power level of a modulation module in said physical layerdevice based on said retrieved configuration parameters; andconfiguring, by said control module, a wave shaping function implementedby a wave shaping module in said physical layer device based on saidretrieved configuration parameters, said wave shaping module applyingsaid configured wave shaping function to a modulated signal generated bysaid modulation module at said configured transmit symbol rate and saidconfigured transmit power level, wherein said configured wave shapingfunction as applied to said modulated signal reduces signal emissionswhen said wave shaped modulated signal is transmitted in a communicationcable in said automotive vehicle.
 2. The method of claim 1, wherein saidmodulation module has a pulse amplitude modulation capability.
 3. Themethod of claim 1, wherein said parameters of said control register aredefined based on signal emission requirements defined for saidautomotive vehicle.
 4. The method of claim 1, wherein said wave shapingfunction is of the form F(z) =a+z⁻¹.
 5. A physical layer device thatcontrols radiated emissions in a data network application in anautomotive vehicle, comprising: a modulation module designed to generatea modulated signal based on a data stream received by said modulationmodule; a wave shaping module that receives said modulated signalgenerated by said modulation module, said wave shaping module shapingsaid received modulated signal in accordance with a wave shapingfunction that is determined using a control signal; and a control moduleconfigured to generate said control signal, said control modulegenerating said control signal in accordance with contents of a controlregister accessible by the physical layer device, said contents of saidcontrol register being used to configure said wave shaping functionimplemented by said wave shaping module to reduce signal emissions in acommunication environment of said automotive vehicle.
 6. The physicallayer device of claim 5, wherein said modulation module has a pulseamplitude modulation capability.
 7. The physical layer device of claim5, wherein said modulation module has a capability of operating atmultiple transmit symbol rates and multiple transmit power levels. 8.The physical layer device of claim 5, wherein said contents of saidcontrol register are defined based on signal emission requirementsdefined for said automotive vehicle.
 9. The physical layer device ofclaim 5, wherein said wave shaping function is of the form F(z)=a+z⁻¹.10. A method in a physical layer device for controlling radiatedemissions in a data network application in an automotive vehicle,comprising: generating, by a modulation module in said physical layerdevice, a modulated signal based on a data stream received by saidmodulation module; shaping, by a wave shaping module in said physicallayer device, said modulated signal to produced a wave shaped modulatedsignal, said shaping being based on a wave shaping function implementedby said wave shaping module; and transmitting, by said physical layerdevice, a signal based on said wave shaped modulated signal onto cablingcontained in said automotive vehicle, wherein said transmission of saidsignal onto said cabling produces reduced emissions, said reducedemissions being based on a pre-configuration of a transmit symbol rateand a transmit power level of said modulation module and said waveshaping function of said wave shaping module, said pre-configurationbeing based on configuration parameters that are retrieved from acontrol register accessible by said physical layer device.
 11. Themethod of claim 10, wherein said modulation module has a pulse amplitudemodulation capability.
 12. The method of claim 10, wherein saidparameters of said control register are defined based on signal emissionrequirements defined for said automotive vehicle.
 13. The method ofclaim 10, wherein said wave shaping function is of the form F(z)=a+z⁻¹.